Residents of downtown Salt Lake City have reported hearing strange music coming from the sewers, prompting some to speculate that the sound may have extraterrestrial origins.
“[It was] really a little creepy, but it was beautiful,” Rosemary Olsen, a musician and inner-city resident who reported hearing an augmented B chord repeatedly outside her window, told news station KSTLV.
Olsen told the outlet that he posted about the noise on the neighborhood app Nextdoor, where other residents reported hearing similar tones.
“A lot of people said, ‘It’s aliens!'” he said.
“Somebody else said ‘Oh, that was my band practicing, it was supposed to be a minor seventh. I guess we blew it.’”
The mystery was cleared up by the Salt Lake City Utilities Department, who said the sound came from the Sewer Line Rapid Assessment Tool, or Sewer RAT.
First used in 2015, the Sewer RAT system sends tones from one end of a maintenance hole to the other; a change in volume indicates that there is a blockage or clearance in the pipe.
“A [transmitter] it will emit the tone and the receiver will hear the tone,” explained Wastewater Collection Manager Steve Terry.
“The receiver, while listening to this tone, will assign a score to it as to how open and unobstructed the pipe is.”
Public Services Director Laura Briefer said the Sewer RAT is a green solution that keeps workers out of tight spaces and away from excess debris.
“We greatly reduce the amount of water and energy required to do a traditional water line assessment,” he said.
Despite the noise, Olsen approves of the innovative Sewer RAT.
“I thought, that’s a very earthly job and they’ve made it ethereal and beautiful,” he said.